My file is 300 Mb and I need to modulate sertain equiment I have placed together in a master file.
If I save a copy and delete what I don’t need, the file stays 300Mb.
I intrigrated a 100Mb file and later erased it, but my file stayed 300Mb??
How can I downsize my masterfile to work faster?
Opening a 300Mb master-file takes about 30sec!!
Hope to get an answer soon 
Kind regards Dennis
First thing to try is Model Info>Statistics>Purge Unused.
Deleting components from the model space doesn’t remove them from the file. You need to purge the unused ones. And then purge unused materials.
There are other things you might be able to do to streamline your model but exactly what depends on the model.